1. Field of the Invention
This invention relates to a multiple-task controller which is able to control a plurality of tasks with an external device, and more particularly to a multiple-task controller in which an external device controls a plurality of tasks through memory input/output devices provided respectively for the tasks.
2. Related Art
A multiple-task controller of this type includes a plurality of tasks and a main task adapted to control those tasks. The tasks are controlled through the main task by an external device, so that their processes are performed, whereby the external device is controlled.
FIG. 3 shows a system comprising a conventional multiple-task controller 110 and an external device 120. The controller 110 includes a main task 111 and a plurality of tasks 112a, 112b, . . . . Those tasks 112a, 112b, . . . are so designed as to perform their own processes. The controller 110 is connected to the external device 120. A remote control signal Sa provided by the external device 120 is applied to the main task 111. A remote control signal Sa provided by the main task 111 is applied to the external device 120. Upon reception of the remote control signal Sa from the external device 120, the main task 111 decodes it and applies a command to a predetermined task 112n (where the suffix "n" means "arbitrary") to cause the latter to perform its own process. The result of the process is applied, as a remote control signal Sa, to the external device 120.
Let us consider the case where, in the above-described system, the external device 120 controls the tasks 112a, 112b, . . . . When, in this case, the external device 120 applies an instruction to the main task 111 by using a remote control signal Sa having predetermined contents, the main task 111 controls a given task 112n (where the suffix "n" means "optional") with a command of language level. The result of the process performed by the task 112n is applied to the main task 111 through a command of language level, and it is converted into a remote control signal Sa, which is applied to the external device 120.
As was described above, commands are used for the control between the main task 111 and the tasks 112a, 112b, . . . ; that is, commands of language level are used to start, stop and hold the tasks.
The commands used in the above-described conventional multiple-task controller are substantially equal in concept to those used in the general computer. Hence, the commands are rather difficult for a person to understand who has no general knowledge of the computer.
On the other hand, in the above-described multiple-task controller, more than ten different remote control signals Sa, such as those for start input and output, and pause input and output, are, in general, provided. Those remote control signals have been determined by the manufacturer. Therefore, for some user, all of them may be unnecessary, and for some other user, they are not adequate.
For instance, in a conventional multiple-task robot controller, commands are used for controlling the tasks.
The commands are the same as those used in the general computer; that is, commands of language level are used to start, stop and hold the tasks.
Hence, the system is rather difficult for a person to understand who has no general knowledge of the computer, and in practice it is rather difficult even for the robot operator to understand.
The object of the above-described conventional system is to divide a job into multiple tasks in the existing computer so that the job is achieved with high efficiency. In the existing computer system, it is unnecessary to stop a task which has been started or to start it again, and therefore the tasks are assigned according to the functions.
On the other hand, with a multiple-task robot controller for controlling robots or the like, its tasks are assigned to the devices, respectively, which are controlled by the controller, and therefore each task requires detailed control. Hence, the existing computer system is unsuitable and functionally insufficient as a controller for controlling robots or the like, and is insufficient in function.